Simplified strip accumulation

ABSTRACT

A simplified strip accumulating system of the type wherein a length of strip is formed into a storage coil composed of an inner set of convolutions and an outer set of convolutions interconnected by a free reverse loop extending between and joining the outermost convolution in the inner set and the innermost convolution in the outer set, whereby the reverse loop will orbit freely in opposite directions between the said sets of convolutions as they are rotated, strip being withdrawn from the inside of the innermost set of convolutions upon rotation of said inner set in one direction, and additional strip being added to the outside of the outer set of convolutions upon rotation of said outer set in the opposite direction, the strip being supported on one edge on a horizontally disposed supporting surface with the inner set of convolutions built-up around an inner roll cage, the outer set of convolutions being formed on a moving supporting surface adapted to impart rotary motion to the strip being coiled, the moving support for the outer set of convolutions being driven in timed relation to the feeding speed of the strip being accumulated, the diameter of the innermost convolution in the outer set being established by the relationship between strip feeding speed and rotational speed of the moving support, thereby providing a free-formed outer set of convolutions to the elimination of an outer roll basket and roll adjusting mechanism heretofore employed to form and support the outer set of convolutions in the storage coil.

United States Patent [191 Miller 1 Jan. 1, 1974 SIMPLIFIED STRIP ACCUMULATION George D. Miller, Middletown, Ohio [73] Assignee: Armco Steel Corporation,

Middletown, Ohio [22] Filed: Feb. 24, 1971 [21] Appl. No.: 118,322

[75] Inventor:

La Tour.... 242/55 La Tour 242/55 Primary ExaminerGeorge F. Mautz Assistant Examiner-Edward J. McCarthy Attorney-Melville, Strasser, Foster & Hoffman [57] ABSTRACT A simplified strip accumulating system of the type wherein a length of strip is formed into a storage coil composed of an inner set of convolutions and an outer set of convolutions interconnected by a free reverse loop extending between and joining the outermost convolution in the inner set and the innermost convolution in the outer set, whereby the reverse loop will orbit freely in opposite directions between the said sets of convolutions as they are rotated, strip being withdrawn from the inside of the innermost set of convolutions upon rotation of said inner set in one direction, and additional strip being added to the outside of the outer set of convolutions upon rotation of said outer set in the opposite direction, the strip being supported on one edge on a horizontally disposed supporting surface with the inner set of convolutions built-up around an inner roll cage, the outer set of convolutions being formed on a moving supporting surface adapted to impart rotary motion'to the strip being coiled, the moving support for the outer set of convolutions being driven in timed relation to the feeding speed of the strip being accumulated, the diameter of the innermost convolution in the outer set being established by the relationship between strip feeding speed and rotational speed of the moving support, thereby providing a free-formed outer set of convolutions to the elimination of an outer roll basket and roll adjusting mechanism heretofore employed to form and support the outer set of convolutions in the storage coil.

13 Claims, 4 Drawing Figures PATENTED H974 3.782.662

saw 1 OF 2 INVENTOR/S GEORGE D. Ml LLER ATTORNEYS PATENTEU H974 3.782.662

saw a or 2- lNVENTOR/S GEORGE D MILLER BY m 55m, and 23 ATTO R N EYS SIMPLIFIED STRIP ACCUMULATION BACKGROUND OF THE INVENTION The present invention is directed to improvements in the type of strip accumulating system disclosed in U. S. Pat. No. 3,506,210, dated Apr. 14, 1970 and entitled Compact Strip Accumulator, and has to do more particularly with a simplification of the system. In accordance with the teachings of the aforementioned patent, the accumulator comprises a supporting structure mounting a centrally disposed circular inner cage of rollers around which an inner set of convolutions of the strip material is accumulated. Spaced outwardly from, and preferably concentric with, the central cage of rollers is a second cage of rollers adapted to contain and form an outer set of convolutions. The basic operating principle of the invention resides in the formation of a free reverse loop of strip which orbits in the space between the inner and outer roll cages to form two sets of convolutions each having the same number of turns at any given time during either feeding or delivery. Thus, a length of strip from a coiler or another source of supply is fed into the accumulating device by a set of driven feed rollers or other drive means positioned to feed the strip in essentially tangential relation to the outer roll cage, the strip being fed to the inside of the rollers making up the outer cage, the rollers acting to guide the strip in a circular path. If it is assumed that the initial direction of feed is in a counterclockwise direction, a free reverse loop is made in the strip before the first outer convolution is completed, i.e., the direction of the strip is reversed and a clockwise winding is begun around the inner roll cage. In order to discharge strip from the device, the leading end of the strip is passed around a guide roll forming a part of the inner roll cage and then around an angularly disposed exit roll or arbor at the center of the device which displaces the strip relative to the coil so that it may be discharged as required for subsequent processing or the like. Once the strip has been threaded through the device in the manner described, strip will be accumulated by feeding it into the device at a greater lineal rate than it is being withdrawn, such feeding movement causing the free reverse loop to move in an orbital path between the inner and outer sets of convolutions. For eachconvolution of strip added to the outer set of convolutions during accumulation, a convolution also will be added to the inner set by the orbiting reverse loop. Conversely, when strip is withdrawn from the device, the orbiting loop changes its direction of movement and for each convolution withdrawn from the inner set, a proportional length of strip will be withdrawn from the outer set and the numerical balance between the sets of convolutions will remain the same.

In the system just described, the feeding of the strip is facilitated by mounting the rollers making up the outer roll cage for limited movement in a substantial radial path, thereby permitting the diameter of the outer roll cage to increase as additional convolutions are added to the outer set. Similarly, the rollers in the inner cage may also be movably mounted so that as the innermost convolutions are removed, the inner roll cage will grow in diameterto prevent collapsing of the remaining convolutions which, in turn, prevent slippage between the convolutions.

While such accumulators have provided significant advantages over the conventional loop tower, loop bit and horizontal loop car systems, as well as coil accumulators of the character taught in U. S. Pat. Nos. 3,258,212 and 3,341,139, which rely on a rotatable table or the like to build-up a coil about a central support, with the withdrawal of the strip dependent upon sliding and collapsing movement of the convolutions, it has now been found that the free loop principle of coil accumulation can be effectively practiced without the use of an outer roll cage to define and support the outer set of convolutions when the accumulator is operated in the horizontal plane, i.e., where the strip is supported on edge on a horizontal supporting surface. Such arrangement materially simplifies the accumulator in that the outer roll cage and its operating mechanism may be effectively eliminated or replaced by a simplified guiding system to assist in containing the strip while the first convolution is being established.

RESUME OF THE INVENTION In accordance with the invention, the strip to be coiled is supported on a horizontally disposed table surrounding a circular cage of rollers around which the inner set of convolutions is formed. The strip material is fed onto the table by means of a set of driven feed rolls or pinch rolls which advance the strip onto the table at the desired rate of speed. Preferably, the table will be in the nature of a turntable adapted to rotate around the inner roll cage, although in a modification of the invention the rotatable table may comprise a se ries of radially disposed driven rollers, preferably of frusto-conical configuration, which also will serve to advance the incoming strip in a circular path as it is fed onto the table by the driven pinch rolls. In either event, the rotary table will be provided with a set of radially disposed idler rolls adapted to underlie the inner set of convolutions, i.e., the set of convolutions built-up against the inner roll cage, thereby permitting the inner set of convolutions to be rotated independent of table rotation when strip is being withdrawn from the accumulator. In this connection, the strip is withdrawn from the device either by means of driven exit rolls or by tension exerted by the processing line or the like to which the accumulated strip is being delivered. While other drive means, inclusive of driven cage rollers, may be employed depending upon the size and structural details of a particular device, it is only necessary that the accumulator be constructed in such a way that the inner set of convolutions can act in an essentially friction-free, independent manner, while the rotary table on which the outer set of convolutions is supported acts to advance the convolutions in a circular path on the table. The only other essential requirement is that no obstruction be presented to the free movement of the reverse loop.

In accordance with the invention, the initial diameter of the outer set of convolutions, i.e., the innermost convolution in the outer set, is determined by the relationship between pinch roll and table rotation speeds. For example, if the pinch rolls are driving the input strip at X feet per minute and the table is rotating at r rpm, the

approximate diameter of the initial convolution in the outer set will be:

Convolution Diameter X/m and this will be true regardless of the table diameter, assuming of course that the table diameter is at least as large as the diameter of the convolution. This equation will not give an exact value; in most cases, the actual diameter will be slightly larger than that predicted for two reasons. First, the strip stiffness will produce a spring effect with the free loop and tend to push the initial convolution outwards. Second, centrifugal force will tend to enlarge the diameter. In addition, the initial diameter of the free loop interconnecting the inner end outer sets of convolutions will be the difference in the radius of the initial convolution in the outer set and that of the inner roll cage..The free loop diameter should be at least 250 times the strip thickness and more preferably 400 to 800 times strip thickness where metallic strip is being accumulated. It may be further noted that as the speed of rotation of the table increases relative to the feeding speed of the incoming strip, the diameter of the convolution being formed will decrease, whereas if the speed of rotation of the table decreases relative to strip feeding speed, the diameter of the resultant convolution will increase. It is thus possible to correlate feeding speed and rotational speed of the supporting table to provide an initial outer convolution of the desired diameter. Since the diameter of the initial convolution may be readily controlled, an outer roll cage is not required to maintain the strip on the table since it will automatically assume the desired diameter in accordance with the foregoing formula.

As a practical matter, however, it is preferred to provide a series of guide rollers surrounding the rotatable table as a precautionary matter and to keep the strip on the table while the first convolution is being established. However, such rolls or other guiding means may be of relatively light construction and may be retracted or removed once the initial convolution has been established.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a somewhat diagrammatic plan view of an accumulator for carrying out the invention, with the inner and outer sets of convolutions in a loaded condition.

FIG. 2 is a somewhat diagrammatic cross-sectional view taken along the line 22 of FIG. 1.

FIG. 3 is a schematic plan view of the accumulator illustrating the manner in which the strip is initially threaded through the device.

FIG. 4 is a schematic view similar to FIG. 3 illustrating the manner in which convolutions are built-up on both the inner and outer sets.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIGS. 1 and 2 of the drawings, the accumulator has a base 1 the upper surface 2 of which mounts rollers 3 which define an inner roll cage surrounded by the rotatable annular table 4 mounted on bearing means 5. The annular rotatable table 4 may be provided with a ring gear 6 which may be engaged by a pinion 7 mounted on the shaft of a variable speed motor 8.

A length of strip material 9 is adapted to be fed onto the table 4 by means of driven pinch rolls l and 11 which will be operatively connected to a suitable variable speed drive means (not shown) so that the feeding speed of the strip may be controlled. As the strip is fed onto the table 4, it will be concurrently formed into a set of outer convolutions l2 and a set of inner convolutions 13 interconnected by a reverse loop 14 which, as will be explained in greater detail hereinafter, orbits in the space between the inner and outer sets of convolutions as strip is added or removed from the coil. Since it is also necessary that the inner set of convolutions 13 be free to rotate independently of the outer set of convolutions, the rotatable table 4 is preferably provided with idler rolls 15 inset into the table to support the inner set of convolutions. The strip is withdrawn from the center of the device by means of a pay-off roll or arbor 16 which is preferably cylindrical in configuration with its axis inclined from the plane of the table at an angle sufficient to provide clearance of the exiting strip over the sets of convolutions. Although the payoff roll 16 is illustrated as a smooth roll, the strip may be scratched as it slides endwise on the roll. The skilled worker will understand that this problem can be avoided by providing the roll surface with small barrel shaped rollers mounted on a helical path as illustrated generally in US. Pat. No. 2,212,006 to Buchanan. Other frictionless means such as balls or gas bearings could also be used. The pay-off roll 16 will normally be free-running with strip removal controlled either by driven exit rolls similar to rolls l0 and 11 or by tension applied by a processing line or the like being fed by the accumulator.

The manner in which the strip is initially threaded through the device can be best understood from FIG. 3 wherein, as shown in solid lines, the strip 9 is led onto the table and passed inwardly through the inner roll cage between a pair of the roller 3, one of which is essentially tangent with respect to payoff roll 16. When so threaded, the pinch rolls l0 and 11 are actuated to feed the strip onto the table, and concurrently the drive motor 8 is actuated to rotate the table 4. As the strip feed continues, the strip will move in a circular path as the table rotates, and the free reverse loop 14 will be formed, as indicated in dotted lines in FIG. 3. It will be noted that the reverse loop 14 tends to initially move toward the periphery ofthe table 4, but as the rotational speed of the table increases, the position of the reverse loop will stabilize and it will travel in a circular path and, as illustrated in FIG. 4, the continued rotation of the table 4 results in the formation of an initial outer convolution 12a and an initial inner convolution 13a, the inner convolution being built-up against the rollers 3 which define the inner roll cage.

As strip feed and table rotation continue, the reverse loop 14 will continue to orbit in a counterclockwise direction, thereby concurrently building up additional convolutions in both the inner and outer sets.

The diameter of the initial outer convolution 12a is established by correlating the speed of rotation of the table 4 to the input speed of the strip 9, as established by the driven pinch rolls 10 and 11. For example, if the inner roll cage has a diameter of 5 feet and the rotatable table 4 has a diameter of 15 feet, and it is desired that the initial convolution 12a in the outer set have a diameter of 10 feet, the speed of rotation of the table 4 to produce an initial outer convolution having a 10 foot diameter may be readily calculated for any given strip feeding speed. If the pinch rolls l0 and 11 are to drive the input strip at 314 feet per minute, the rotational speed of the table would be calculated as follows:

where r equals rpm. In the above equation:

and consequently for a strip feed of 314 feet per minute, the table 4 would be rotated at a speed of rpm in order to establish a 10 foot diameter for the initial outer convolution 12a. It will be evident that as strip feeding speed increases, the speed of rotation of table 4 must be increased proportionately if the diameter of the initial convolution is to be maintained at 10 feet. Conversely, if the feeding speed of the strip is decreased, there must be a proportional decrease in speed of table rotation to maintain the desired diameter of the initial convolution. It will also be evident that the diameter of the initial convolution may be either increased or decreased, as desired, by varying the ratio of strip feeding speed to table rotation. For example, if it is desired that the initial convolution in the outer set have a diameter of 12 feet, and assuming that the strip feeding speed is to remain at 314 feet per minute:

Theoretically, as long as the diameter of the rotatable table is greater than the desired diameter of the initial convolution, the incoming strip will remain on the table without external guide means, such as an outer roll cage. However, if the rotatable table is to be held to near minimum diameter, some form of external guide means is desirable to insure that the strip remains on the table while the first convolution is being established. Such guide means need not be massive or mounted to expand and contract with the outer set of convolutions, but rather may simply comprise an abutment means to insure retention of the strip on the table as the initial convolution is being formed. To this end, and as illustrated in FIGS. 1 and 2, a series of guide rollers 19 may be arranged about the periphery of the rotatable table 4 to restrain the strip. Such rollers may be retractable so that they may be displaced to an inoperative position once the initial convolution is formed; and if desired, they may be lightly spring loaded toward the center of the device to assist in containing the developing coil. Obviously, sweep means or the like could be employed since there will be only slight, if any, contact between the strip being accumulated and the guide means.

In order that the outer set of convolutions may be developed without sliding the coil on the table, the drive means for the table should be designed to develop constant torque rather than constant speed. If the feeding speed of the strip remains constant, it will be evident that a drag will be created as the diameter of the outer set of convolutions increases with the addition of each succeeding convolution. The pinch roll drive feeding the strip could also be driven with a constant torque rather than a constant speed. However, to the extent that compensating adjustments may be required, either the feeding speed of the strip or the speed of rotation of the table, or both, maybe varied as required to maintain the integrity of the outer set of convolutions without slippage.

In the operation of the device, it should now be evident that with each revolution of the orbiting reversed loop 14 in a counterclockwise direction, one turn of strip will be added to each set of convolutions stored on the device. When the device is fully loaded, i.e., maximum storage achieved, the strip feed and table rotation will be simultaneously stopped. The device is now ready to deliver a continuous supply of strip. As the strip is withdrawn from the device, it passes around the pay-off roll 16 and the convolutions in the inner set begin to rotate relative to the inner roll basket as the innermost convolution is drawn inwardly between the pair of guide rollers 3, the inner set of convolutions being freely rotatable on the supporting idler rolls l5. Simultaneously with the rotation of the innermost set of convolutions, the reverse loop 14 begins to move in a clockwise direction, thereby peeling the innermost convolution from the outer set. The peeling action is such that for each convolution of strip removed fromthe inner set, a portion of a convolution will be transferred from the outer to the inner set, but the numerical balance between the number of convolutions in the inner and outer sets will remain the same, with the number of convolutions in each set diminishing at the same rate.

If strip delivery is to remain continuous, it will be necessary to add additional strip to the device, and the pinch rolls l0 and 11 and the rotating table will again be actuated. Since the idler rolls l5 mount the inner set of convolutions for rotation independently of the rotatable table 4, rotation of the table does not interfere with the rotation of the inner set of convolutions as strip is withdrawn from the device. However, the speed and even the direction of movement of the reverse loop will depend upon the relative input and exit speeds of the strip. That is, if the lineal speed of the strip feed exceeds the lineal speed of the strip discharge, the reverse loop will again begin to move in a counterclockwise direction, thereby building up and storing additional convolutions of strip. If, however, the lineal speed of strip discharge exceeds the lineal speed of strip feed, the reverse loop will move in a clockwise direction, albeit at a slower rate. Of course, if the input and discharge speeds are equal, the system will be in balance and the reverse loop will remain essentially stationary. In normal operation, the discharge speed of the strip will be less than the delivery speed, so that strip delivery may be interrupted, as may be required to add additional lengths of strip to the continuous supply, without interrupting strip discharge, as where the discharge strip is being delivered to a continuous processing line or the like.

As should now be evident, the instant invention provides a simplified accumulating system for strip material which eliminates the necessity for an outer roll basket to control strip build-up, together with the supporting mechanism for expanding and contracting such outer roll cage. By controlling the speed of the strip as it is fed onto the table, the operator may readily adjust the location of the inner convolution in the outer set in accordance with strip thickness and the number of convolutions which are to be stored. While primarily intended for the accumulation of metallic strip, it will be evident that the utility of the invention is not so limited and may be employed to accumulate diverse kinds of strip materials capable of being handled and stored in coil form.

Modifications may be made in the invention without departing from its spirit and purpose. For example, while stationary rollers may be utilized to form the inner roll cage, the inner roll cage may be made expansible in the manner taught in U.S. Pat. No. 3,506,210.

Similarly, the rotatable table may be replaced by a series of radially disposed driven rollers which will serve as a support for the strip and at the same time impart the desired rotary motion. Preferably, such driven rollers will be of tapered configuration, i.e., frusto conical, so that their lineal speed will vary progressively along the length of the rollers, thereby enabling the operator to place the initial convolution in the outer set at any desired diameter.

It will also be understood that numerous controls may be provided for operating the device, although essentially they may be relatively simple. Thus, the device may be operated manually, the operator simply stopping feeding movement and table rotation when a predetermined number of convolutions has been accumulated, strip feed and table rotation being resumed when the number of convolutions has diminished to a specific -point. On the other hand, automatic operation may be provided with a minimum of controls, such as a limit switch positioned near the point of strip entry which may be utilized to detect the removal of the outermost convolution in the outer set and activate the feed rolls and rotary table to initiate accumulation. Alternately, such control may comprise an edge-sensing member positioned to detect the movement of the strip edge, and it may be located so as to actuate the feed rolls and rotary table upon removal of the last convolution or depletion of the outer set of convolutions to any given number of turns. lf desired, a photocell or like detector may be located in advance of the feed rolls to detect the end of the strip before it reaches the rolls so that additional strip may be added.

Controls also may be provided to arrest the feeding of strip to the device when a predetermined number of convolutions have been built-up on the table. Thus, limit switches can be arranged so as to stop the movement of the feed rolls and table when maximum accumulation has occurred. Similarly, such controls may include means for stopping the processing line being fed by the accumulator in the event of a breakdown which would result in the presence of insufficient strip to satisfy the demand of the processing line. It also may be pointed out that in situations wherein the strip material being accumulated is quite flexible, it may be necessary to provide additional support for the outer set of convolutions. Such support may comprise hold-down means adapted to overlie the strip, or the table itself may be provided with a frictional gripping surface or magnetic inserts may be employed if the strip material is ferromagnetic. While the inner and outer sets of convolutions will normally be in the same plane, they may be offset relative to each other to facilitate strip withdrawal or other design feature.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a method of accumulating strip material in which a length of strip is formed into a storage coil having an inner set of convolutions and an outer set of convolutions being interconnected by a reverse loop extending between and joining the outermost convolution in the inner set and the innermost convolution in the outer set, and in which strip is withdrawn from the inside of the innermost set of convolutions by rotating said inner set in one direction, and additional strip is fed to the outside of the outer set of convolutions by rotating said outer set in the opposite direction, the steps of forming said sets of convolutions on a horizontally disposed supporting surface by feeding said strip onto the supporting surface on edge at a predetermined speed x, and concurrently imparting rotary motion to said strip as it is fed onto said supporting surface, said strip being rotated at a rotational speed r in accordance with the equation:

where d is the desired diameter of the innermost convolution in the outer set, whereby to free-form the innermost convolution in the outer set to substantially the diameter d in the absence of external peripheral guide means to establish the diameter of the said innermost convolution in the outer set.

2. The method claimed in claim 1 including the step of forming said innermost set of convolutions around and against a centrally disposed roll cage, and causing the innermost convolution in said outer set to rotate a circular path around and in spaced relation to said roll cage.

3. The method claimed in claim 2 including the step of imparting rotary motion to said outer set of convolutions by supporting said outer set of convolutions on a moving support.

4. The method claimed in claim 3 wherein said moving support comprises a rotatable table having its axis of rotation coinciding with the center of said inner roll cage.

5. The method claimed in claim 4 including steps of supporting said inner set of convolutions for rotation independently of the rotation of said rotatable table on which said outer set of convolutions is supported, whereby said inner set of convolutions may be rotated independently of said outer set of convolutions.

6. In a strip accumulating device wherein a length of strip is formed into a storage coil composed of an inner set of convolutions and an outer set of convolutions interconnected by a reverse loop, a horizontally disposed support for receiving a length of strip, an inner annular roll cage positioned centrally of said support, feed means for delivering strip on edge onto said support at a predetermined speed, driven means forming a part of said support, said driven means being engageable with the strip edge to impart rotational movement to said strip at a predetermined rate of rotation, and means for varying the relationship between the feeding speed of the strip and the speed of rotation of said strip, whereby the inner set of convolutions may be built-up around said roll cage and said outer set of convolutions builtup on said support in spaced relation to said inner set of convolutions.

7. The strip accumulating device claimed in claim 6 wherein said support includes means mounting the inner set of convolutions for rotation independently of said driven means for imparting rotational movement to said strip as it is fed onto said support.

8. The strip accumulating device claimed in claim 7 wherein the driven means for imparting rotational movement to said strip comprises a rotatable table surrounding said inner annular roll cage.

9. The strip accumulating device claimed in claim 8 wherein the means mounting the inner set of convolutions for rotation independently of the outer set comprises idler rolls inset in said rotatable table and projecting radially outwardly from said annular roll cage.

10. The strip accumulating device claimed in claim 9 including guide means at the periphery of said rotat- 11 including a variable speed drive means operatively connected to said driven means.

13. The strip accumulating device claimed in claim 11 wherein the means for varying the relationship between the feeding speed of the strip and its speed of rotation comprises variable speed drive means operatively connected to said driven means. 

1. In a method of accumulating strip material in which a length of strip is formed into a storage coil having an inner set of convolutions and an outer set of convolutions being interconnected by a reverse loop extending between and joining the outermost convolution in the inner set and the innermost convolution in the outer set, and in which strip is withdrawn from the inside of the innermost set of convolutions by rotating said inner set in one direction, and additional strip is fed to the outside of the outer set of convolutions by rotating said outer set in the opposite direction, the steps of forming said sets of convolutions on a horizontally disposed supporting surface by feeding said strip onto the supporting surface on edge at a predetermined speed x, and concurrently imparting rotary motion to said strip as it is fed onto said supporting surface, said strip being rotated at a rotational speed r in accordance with the equation: r x/d pi where d is the desired diameter of the innermost convolution in the outer set, whereby to free-form the innermost convolution in the outer set to substantially the diameter d in the absence of external peripheral guide means to establish the diameter of the said innermost convolution in the outer set.
 2. The method claimed in claim 1 including the step of forming said innermost set of convolutions around and against a centrally disposed roll cage, and causing the innermost convolution in said outer set to rotate a circular path around and in spaced relation to said roll cage.
 3. The method claimed in claim 2 including the step of imparting rotary motion to said outer set of convolutions by supporting said outer set of convolutions on a moving support.
 4. The method claimed in claim 3 wherein said moving support comprises a rotatable table having its axis of rotation coinciding with the center of said inner roll cage.
 5. The method claimed in claim 4 including steps of supporting said inner set of convolutions for rotation independently of the rotation of said rotatable table on which said outer set of convolutions is supported, whereby said inner set of convolutIons may be rotated independently of said outer set of convolutions.
 6. In a strip accumulating device wherein a length of strip is formed into a storage coil composed of an inner set of convolutions and an outer set of convolutions interconnected by a reverse loop, a horizontally disposed support for receiving a length of strip, an inner annular roll cage positioned centrally of said support, feed means for delivering strip on edge onto said support at a predetermined speed, driven means forming a part of said support, said driven means being engageable with the strip edge to impart rotational movement to said strip at a predetermined rate of rotation, and means for varying the relationship between the feeding speed of the strip and the speed of rotation of said strip, whereby the inner set of convolutions may be built-up around said roll cage and said outer set of convolutions built-up on said support in spaced relation to said inner set of convolutions.
 7. The strip accumulating device claimed in claim 6 wherein said support includes means mounting the inner set of convolutions for rotation independently of said driven means for imparting rotational movement to said strip as it is fed onto said support.
 8. The strip accumulating device claimed in claim 7 wherein the driven means for imparting rotational movement to said strip comprises a rotatable table surrounding said inner annular roll cage.
 9. The strip accumulating device claimed in claim 8 wherein the means mounting the inner set of convolutions for rotation independently of the outer set comprises idler rolls inset in said rotatable table and projecting radially outwardly from said annular roll cage.
 10. The strip accumulating device claimed in claim 9 including guide means at the periphery of said rotatable table for maintaining the strip on said table during start-up of the device.
 11. The strip accumulating device claimed in claim 6 wherein the means for varying the relationship between the feeding speed of the strip and its speed of rotation comprises variable speed driven means operatively connected to said strip feed means.
 12. The strip accumulating device claimed in claim 11 including a variable speed drive means operatively connected to said driven means.
 13. The strip accumulating device claimed in claim 11 wherein the means for varying the relationship between the feeding speed of the strip and its speed of rotation comprises variable speed drive means operatively connected to said driven means. 